Ti-22Al-25Nb合金板材气压胀形实验及数值模拟

Experiment and Numerical Simulation of Ti-22Al-25Nb Alloy Sheet by Gas Bulging

摘要:

通过气压胀形实验和数值模拟研究了Ti-22Al-25Nb合金板材在高温下的热成形行为，并分析了在930和970 ℃下的胀形球壳形状和壁厚分布，讨论了胀形部分的微观结构和力学性能。结果表明，在胀形初期，胀形球壳接近球面，随胀形高度的增加逐渐椭球化。在930和970 ℃下，最终胀形高度分别达到46.25和49.85 mm，壳顶的曲率半径分别达到49.33和49.19 mm。胀形部分壁厚不均匀，从底部至顶部逐渐减小。变形温度对球壳形状影响较大，在930 ℃时胀形局部形状更加不均。在相同的胀形高度下，930 ℃下的胀形球壳曲率半径较小且壁厚减薄率较高。此外，在930 ℃胀形过程中，O相析出并球化，导致O型、V型空洞的产生且硬度下降。而在970 ℃胀形后，微观组织分布均匀，O相在冷却过程中以层片形式析出，强化了胀形件。

Abstract:

The hot formability of Ti-22Al-25Nb alloy sheet at elevated temperatures was studied through the gas bulging experiments and numerical simulation. The distributions of bulging shell shape and wall thickness at 930 and 970 °C were analyzed. The microstructure and mechanical properties of the bulging part were discussed. Results show that the bulging shell is close to the spherical surface in the initial bulging stage, and it gradually becomes ellipsoid with increasing the bulging height. At 930 and 970 °C, the final bulging height reaches 46.25 and 49.85 mm, and the curvature radius of shell top reaches 49.33 and 49.19 mm, respectively. The wall thickness of bulging part is inhomogeneous: it gradually decreases from the bottom region to the top region. The deformation temperature strongly affects the shape of bulging part: the partial bulging shape is more inhomogeneous at low temperature of 930 °C. Under the same bulging height, the curvature radius of bulging is lower and the thinning ratio is higher at 930 °C. In addition, the O phase is precipitated and spheroidized during bulging at 930 °C, which causes the generation of O type and V type cavities and the reduction in microhardness. However, the microstructure is uniformly distributed after bulging at 970 °C. O phase is precipitated during the cooling process in lamellar morphology, which strengthens the bulging part.